1. Technical Field of the Invention
This invention relates generally to wireless communication devices and more particularly to phase locked loops.
2. Description of Related Art
CMOS (complimentary metal oxide semiconductor) technology has enabled the integration of very complex circuitry into very small integrated circuit packages. However, some components must remain off-chip due to the precision needed, value flexibility needed, and/or the excessive die area required to implement the component on-chip. For instance, components of a loop filter of a local oscillation generator (which includes a phase locked loop) used in radio frequency integrated circuits by both the transmit and receive sections are off-chip. While the off-chip components allow for greater flexibility in value selection, greater precision, and/or die area savings, it comes at the cost of pin count and increased noise.
As is known, at radio frequency (RF) frequencies (e.g., in the gigahertz), coupling between integrated circuits and external components via pins and board traces adds unwanted parasitics (e.g., inductance and capacitance) to the loop filter that adversely effect the performance of the local oscillation generator and hence adverse effects the overall performance of the radio frequency integrated circuit.
Therefore, a need exists for an on-chip loop filter for use within a local oscillation generator that provides similar advantages as off-chip components and minimizes the disadvantages.